This invention relates to apparatus for applying tensile stress to a fiber and more particularly to a machine for pulling and strength testing an optical waveguide.
The increased burden on communication systems has fostered the development of high capacity systems using optical waveguides. These optical waveguides are constructed of a transparent dielectric material such as glass. They consist of a central core surrounded by a cladding having an index of refraction less than the index of refraction of the core. Light propagates along the waveguide. Recently, optical waveguides having very low attenuation per unit length have been developed. For example, the Maurer et al U.S. Pat. No. 3,659,915, and Keck et al U.S. Pat. No. 3,711,262 describe an optical waveguide comprising a core and a cladding layer.
In the fabrication of optical waveguides, the waveguide is heated and drawn into its final form. Any imperfections in the surface of the waveguide can result in fracture of the waveguide during use. Waveguides must be tested by applying tension to detect these flaws. Prior art tensile testers use clamps which often abrade the surface of the waveguide, thereby causing flaws during the testing. Also, prior art tensile testers test the waveguide to destruction. Because of this, often only a small portion of the waveguide is actually tested.